Triiodide (I.sub.3.sup.-) anion exchange resins for disinfecting water are described in Taylor, et al. Appl. Microbiol. (1970), 20:720-722, U.S. Pat. Nos. 3,817,860 and 3,923,675, and Fina and Lambert, "Proceedings, Second World Congress, International Water Resources Association", Vol. II pp. 53-59, New Delhi, 1975. The disinfectant resins were prepared by contacting an anion exchange resin in chloride or sulfate form with a sodium or potassium triiodide solution. Typical concentrations of the triiodide ion were around one molar, and the contacting was carried out at room temperatures. The cited patents also describe alternative procedures. In one procedure (U.S. Pat. No. 3,817,860, column 5, line 74, and column 6, line 5), the anion exchange resin, such as a quaternary ammonium resin, is first converted from the chloride or sulfate form to an iodide form by being contacted with a potassium iodide solution. The resin is then contacted with a triiodide solution or with elemental iodine (U.S. Pat. No. 3,923,665, column 3, lines 62-69).
Methods for preparing quaternary ammonium anion exchange resin triiodide disinfectants were reviewed by Hatch, et al., Ind. Eng. Chem. Prod. Res. Dev. (1980), 19:259-263. If quaternary ammonium anion exchange resins as supplied by the manufacturer contain unconverted tertiary amine groups, they can be remethylated by reaction with methyl iodide or dimethyl sulfate. However, most strong base anion exchange resins are supplied in substantially fully methylated form. A fully quaternarized resin, for example, can provide more stable triiodide disinfectants. In one of the methods described ("Method A"), enough aqueous triiodide ion to the resin was used to convert 97% of the anion sites. The triiodide solution was prepared with the stoichiometric amounts of potassium iodide and iodine, which were dissolved "in a near-minimum amount of water". The solution was stirred with the resin beads for 24 hours to complete the conversion. No heating is described so it can be assumed these procedures were all carried out at room temperature.
Pentaiodide quaternary ammonium resins and their properties were described by Lambert, et al in Ind. Eng. Chem. Prod. Res. Dev. (1980) 19:256-258. An I.sub.5.sup.- resin was prepared from an I.sub.3.sup.- resin by dissolving iodine in heated water and passing the water through the resin by a continuous recycle procedure. The I.sub.3.sup.- resin used as a starting material was prepared by a previously disclosed procedure in which an aqueous solution of triiodide is applied to the resin. It was found that at the recommended recycle temperature of about 60.degree. C., the I.sub.5.sup.- resin could be produced in as little as 10 hours, but only on a small scale. This reference also described the preparation of an I.sub.7.sup.- resin from the I.sub.5.sup.- resin by a similar recycle procedure.
U.S. Pat. No. 4,238,477 discloses a procedure for preparing polyiodide quaternary ammonium anion exchange resins similar to that described in Lambert, et al. (1980), cited above. The patent states that the procedure can be used to prepare I.sub.3.sup.-, I.sub.5.sup.-, I.sub.7.sup.- or mixed polyiodide resins. Mixed polyiodide resins are also described in U.S. Pat. Nos. 4,187,183 and 4,190,529, a mixed polyhalide resin is disclosed in U.S. Pat. No. 4,420,590.
The mixed polyiodide resins disclosed in (U.S. Pat. Nos. 4,187,183 and 4,190,529 contained both I.sub.3.sup.- and I.sub.5.sup.- groups. From 40 to 80% of the exchange sites were I.sub.3 and from 1 to 30% were I.sub.5 groups. The method of this preparation was similar to that described in Hatch, et al. (1980), cited above. Resin beads were placed in a container and covered with a minimum volume of water. A separate container of crystalline iodine and potassium or other water-soluble iodized salts was solubilized in just enough water to dissolve the reactants (col. 2, lines 35-36). After the reactants had completely dissolved, the solution was added to the water containing the resin, mixed therewith for sufficient time to complete adsorption of the polyiodide ions on the exchange sites of the resin, for example, from 24 to 72 hours. No molalities or molarities are specified with respect to the reaction solution and there is no disclosure of heating the reaction solution. Presumably, therefore, all steps of the method were carried out at room temperature.
Triiodide and pentaiodide resins function as broad spectrum bacteriacides against both Gram-positive and Gram-negative bacteria in water, and also against RNA and DNA viruses: Lambert, et al. (1980), cited above; and Fina, et al., Appl. Environ. Microbiol. (1982) 44:1370-1373. It has also been reported the pentaiodide or mixed polyiodide resins are effective as disinfectants against water-borne cysts of Giardia muris. and Giardia lamblia. Marchin, et al., Appl. Envron. Microbiol. (1983), 46:965-969.
Despite the great potential for I.sub.3.sup.-, I.sub.5.sup.- and mixed polyiodide anion exchange resins for bacterial, viricidal, and Giardia disinfection of drinking water, these resins have thus far received only limited use. The available methods of producing polyiodide resins have not been adaptable to large scale economical production. The continuous cycle procedure using dilute solutions of iodine in warm water as described in U.S. Pat. No. 4,238,477 and Lambert, et al. (1980), cited above, have been limited to small scale production. The method is labor intensive and time consuming. For producing a mixed polyiodide resin a two-stage procedure is required in which the I.sub.3.sup.- resin is first produced and then partially converted to include I.sub.5.sup.- sites. Specially designed equipment is required for use in cycling a large volume of water at 50.degree.-60.degree. C. for as long as three to four days to produce the mixed resin. Even with careful preparation by this method, a resin of defined characteristics cannot be reliably produced For example, when a mixed resin containing I.sub.3.sup.- and I.sub.5.sup.- groups in preselected proportions is desired, the resulting product will contain a variable amount of I.sub.7.sup.- groups.